A stent is an artificial “tube” or cylindrical device inserted into a natural passage in the body to prevent a localized flow constriction. For example, a coronary stent is a cylindrical device placed in a coronary artery that supply the heart in order to keep the arteries open in the treatment of coronary heart disease. Traditionally, coronary stents consisted of a metal framework that could be placed inside the artery to help keep it open. However, as the stent is a foreign object, it incites an immune response. This may cause scar tissue to rapidly grow over the stent. In addition, there is a strong tendency for clots to form at the site where the stent comes into apposition with the arterial wall. To address these issues, a new generation of stent has been developed with biodegradable polymers.
A polymer stent can be manufactured using the process of laser ablation of a polymer tube, a process in which a laser device irradiates the polymer tube with a laser beam. The irradiation helps to remove closed contoured sections from the polymer tube, thereby creating a polymer framework of the stent.
However, a number of issues can occur when cutting a specific pattern in a polymer tube. For example, the polymer tube may not exactly follow the pattern programmed in the laser device because of the torsion occurring as the polymer tube is moved around by a holding mechanism. Another issue may relate to the polymer tube bending as the high-pressure process gas is used to remove debris during the athermal ablation. Yet another issue may relate to the polymer sections bending as they are being cut away.
The fabrication of cardiovascular stents or other medical devices designed for implantation in the human body require extreme precision in feature size and location and the current generation of tube cutting workstations are inadequate to achieve the necessary fidelity to a computer generated design when machining novel materials (e.g. polymers).